Late gestation fetal sheep will be treated to create systemic and pulmonary arterial hypertensions. One group will have high circulating angiotensin-II levels. There will be two normotensive control groups, one with normal and one with low angiotensin-II. The animals will be studied as fetuses, as newborns and as young adults. Circulatory measurements will include arterial pressures, right and left atrial pressures and cardiac outputs. We will also make plasma renin activity/renal ar6terial pressure response curves and measurements of glomerular filtration rates. Analytical measurements will include plasma renin activities, circulating angiotensin-II levels, catecholamines, plasma protein and blood hemoglobin concentrations, blood gases, osmolalities and electrolytes. Coronary pressure-flow relations will be determined under anesthesia with and without chemical dilation by means of adenosine infusions to determine coronary reserve. The animals will be killed for structural studies of heart and kidney. It is anticipated that prenatal hypertensions will produce lasting circulatory abnormalities later in life.